We speak naturally and can sometimes alter our voice for circumstances. My children tell me I have a 'telephone' voice. I start speaking in a posh way that isn't how I normally sound. People might also have fun trying to speak in a different accent although it is usually possible to see they are acting unless they are professional actors.
Your writing will also have a feel to it that is distinctly yours. You will eventually write in a way that suits your personality and also the content of the article you are writing. However, this may not come to us as naturally as speaking.
Finding your writer's voice takes time and making sure you keep it for at least the length of an article is harder. It will be a style of writing that is unique to you and the things you put into print. You will need to take time to see which style suits your personality and temperament and eventually come to recognise this as your own.
When you have found your voice you might still alter it for different types of articles just as I alter my voice (and you probably do too,) on the telephone.
Some people say that the writer's voice comes naturally. I think this is true to some extent, but once you know what makes your writing distinctive you can alter it to suit the occasion. However, when you do that you will need to be careful as your natural voice will tend to try and break through and you may end up with a poor article because you have used two or more styles of writing.
Always check your article remains in the same voice unless you have a genuine reason for altering the style that actually enhances what you have to say.
The best way to find out what your voice is is to indulge in some free flow writing and then examine the style within the piece you have created.